Oscillometric monitoring system for sphygmomanometers



April 25, 1967 M, A- BUFFINGTON OSCILLOMETRIC MONITORING SYSTEM FOR SPHYGMOMANOMETERS Filed Jan. 16, 1964 INVENTOR.

MARVIN A. BUFFINGTON ATTORN YS United States Patent 3,315,662 OSCILLOMETRIC MONITORING SYSTEM FOR SPHYGMOMANOMETERS Marvin A. Buflington, 1061 Lauder Road, Cleveland, Ohio 44124 Filed Jan. 16, 1964, Ser. No. 338,240 7 Claims. (Cl. 1282.05)

This invention is directed to an ultrasensitive sphygmomanometer monitoring system of the oscillometric type. This invention particularly relates to such a system wherein a novel electronic oscillometric cuff is employed.

This invention can best be understood by distinguishing between the basic monitoring systems used in present medical practice. The auscultatory system employs the principle wherein a device detects sounds which are pro duced within the body by the circulation of the blood and uses these sounds as a means of detecting blood pressure in conjunction with a sphygmomanometric cuff. Determination of blood pressure is made by inflating the cuff so as to ascertain the blood pressure as the cuff pressure is released by listening to the returning sounds. Specifically the oscillometric technique utilizes the pulse indication generated in the inflatable bag and manometer of the sphygmomanometric system. By means of the electronic system in the cuff which detects the pulse of the arterial system of the body, pulse indications are generated at all pressures in the cuff and come to a peak at the mean arterial value.

The oscillometric technique is presently employed in medical practice in tests for pulse values in various parts of the body for determining arteriosclerotic conditions and in testing for a basal pulse in critical or surgical patients when an ordinary blood pressure cannot be obtained by the auscultatory method.

The present oscillometric systems, however, have not been used as extensively in medical practice as desired because of the inability of such mechanical systems to provide a significant pulse indication on the present read out means. This inability is a direct result of the fact that the presently available sphygmomanometers do not possess a sufficiently high degree of sensitivity at low cuff pressures.

It is an object of this invention therefore to provide an ultrasensative oscillometric device whereby the abovementioned problem of the prior art is avoided.

Another object of this invention is the provision of an ultrasensitive sphygmomanometer wherein an electronic oscillometric cuff of a special design is utilized.

Other objects, features, and advantages of this invention will become apparent to those skilled in the art in view of the following more detailed description of the invention.

These and other objects are achieved by means of this invention in which an ultrasensitive electronic means is provided for observing pulse in the sphygmomanometric system. Specifically, the electronic means comprises a fabric cuff of the Tycos type which has an inflatable bag member positioned therein and a transducer element inserted Within the cuff and against the face of the inflatable bag. The transducer element has a flexible focusing disc attached to it which serves, as will be more fully explained, to give the transducer an increased degree of sensitivity.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail a certain illustrative embodiment of the invention, this being indicative, however, of

but one of the various ways in which the principle of the invention may be employed.

In said annexed drawings:

FIG. 1 of the drawings is a fragmentary plan view showing schematically the electronic sensing device inserted into the cuff of a sphygmomanometer;

FIG. 2 is a fragmentary perspective view showing in detail the parts of the electronic sensing device and its relationship relative to the inflatable bag and cufl, which is illustrated broken away;

FIG. 3 is an enlarged fragmentary detail view showing the connection between the focusing disc and the flexible grid; and

FIG. 4 is a fragmentary view showing, in cross section, the sphygmomanometer of this invention in operative position on an extremity of the body.

Referring now to FIG. 1, the numeral 1 designates a fabric sphygmomanometric cuff with a pocket P formed therein. Broken lines 3 and 4 show the transducer element and flexible disc member respectively of the electronic sensing device positioned within pocket P. Numeral 10 designates a cable which is connected to the transducer element 3 and which has an electrical connector 11 thereon which is capable of being operatively attached to an observational medium (not shown) such as an electrocardiograph, a cardiac monitor, or an electronic meter of any of the many varieties presently available. Also shown in FIG. 1 is a pressure tube 5 with standard valve means B and bulb member 6 attached thereto which is connected to the fabric cuff and the inflatable bag member therein for creating pressure within the cuff and bag during the operation thereof. The usual gauge means G is also shown connected to cuff 1 for observing the blood pressure.

In FIG. 2, the numeral 2 designates the inflatable bag member positioned within the cuff 1. Transducer element 3 is positioned with its face in contact with the face of inflatable bag 2. A thin flexible focusing disc 4 (made from any flexible plastic such as polyethylene or similar material) is positioned between the face plate and back-up plate of the transducer element. Focusing disc 4 is attached to the transducer by means of fasteners such as machine screws and nuts, which are illustrated on the drawings at 7. Such fasteners 7 extend through the backup plate 8 of the transducer. The disc 4 may then be sandwiched between the main body 9 and the back-up plate 8 of the transducer. In this manner, a disc 4 can be attached to a conventional sensitive electronic pressure transducer which may be of the piezo electric type so that the main body 9 thereof containing the sensitive face F will be substantially centered on the disc.

Referring now additionally to FIG. 3, focusing disc 4 is also attached to a flexible locating screen or grid 12 by a plurality of flexible tab members 13 which are wrapped around bars 14 of the grid 12 and fastened with round head machine screws 15 and nuts 16- thereto. The distal ends of the tabs 13 may be provided with b uttonholes which snap over the round heads of screws [[5 releasably to secure the grid to the disc. As indicated, two diametrically opposite tabs 13 are provided on each side of the disc, although further such fasteners may be provided.

Grid 12 is preferably made of nylon, but can be of any suitable resilient plastic material. As shown, grid 12 extends laterally beyond focusing disc 4 and transducer element 3. The function of the grid is to standardize the position of the disc and the transducer Within cuff 1 without being fastened thereto, the grid being rolled up or wrapped around the transducer prior to insertion in pocket P and unrolled after insertion therein.

In FIG. 4, the cuff 1 is shown in cross section posi- Jned on an extremity of the body 17 such as an arm, g, etc. as the case may be. The inflatable bag 2 is Jsitioned such that it is adjacent the extremity 17 and z-parated therefrom only by fabric cuff 1, with the 'ansducer element 3 in contact with the inflatable bag n the side thereof opposite that in contact with the xtremity. In this view, the bag 2 is inflated (by the ulb member 6) thereby forcing flexible disc 4 to ex, as indicated to a concave form. When disc 4 l in this position, it will cause the pulse waves (indiated by the arrows in FIG. 4) which are emitted from xtremity 17 through inflatable bag 2 to be reflected by he flexed disc 4 back against the inflatable bag and ransducer element 3 thereby focusing the pulse waves lgainst the transducer element and increasing the pick-up .ensitivity thereof.

The oscillometric system described above operates as follows. The sphygmomanometric cuff 1 is wrapped around an extremity of the body 17 in the manner illus- :rated in FIG. 4. The electrical connector 11 which is attached to cable of the transducer is connected to a. suitable observational medium, not shown. The inflata'ble bag 2 is then pumped up through bulb 6 and pressure tube 5 to a suitable pressure. Since the transducer element 3 is in contact with the inflated bag 2, and since focusing disc 4 is in its flexed position, the transducer detects the pulsations and transduces them into electrical energy. This energy is introduced into the observational medium and amplified therein so that the pulsations, which are usually seen as small deflections in the usual oscillometric technique, are now displayed on the observational medium as large or delineated pulsations as desired to such an extent that the pulsations can be classified as to characteristics diagnostically or measured to be used as a coeflicient of quantitative blood pressure at any cuff pressure.

It is thus seen that the present invention, as described, provides an ultrasensitive electronic oscillornetric system for detecting (pulsations which utilizes existing medical techniques, merely being adapted to the existing syhy,,- momanometric system, without inhibiting or altering the existing equipment.

Numerous advantages in the form of new practical and badly needed clinical techniques are derived from the *ultrasensitive monitoring system of the present invention. It is now possible to undertake precise quantitative and qualitative evaluations of circulatory defects and qualities in all types of patients. Second, the present invention provides a means of determining a type of blood pressure in an infant or small child which has not heretofore been clinically practical. Third, the oscillometric system herein described provides a means for detecting pulse per se in the critical or questionable case when a blood pulse is not detectable in the usual auscultatory manner. The present invention also provides a simple and practical oscillometric technique for monitoring surgery on arterial graphs and blocks, as well as for determining oscillometric (mean arterial) blood pressure for critical and anesthetic usage. The oscillometric system described also makes it possible to determine a type of blood pressure on animals such as dogs and cats upon which it is not practical to use a stethoscope. In addition to the above advantages, the monitoring system described establishes a method for providing the continuous blood pressure by an oscillometric system where in a measured pulse amplitude is used as a coefficient of systolic blood pressure at low cuff pressures such as 20 millimeters of mercury which can be tolerated for longer periods of time than usual.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims, or the equivalent of such, be employed.

I, therefore, particularly point out and distinctly claim as my invention:

1. Apparatus for monitoring vascular pressure variations, comprising constricting means encircling a portion of a vascular subject, said constricting means comprising a retaining member, an inflatable bag member within the retaining member and means for inflating the inflatable' bag member,

a transducer element positioned within said constricting means between the bag member and the retaining member and responsive to fluid flow variations to emit a signal proportional thereto,

a focusing element positioned adjacent said transducer element on the side of said transducer element remote from the inflatable bag for reflecting energy from the flow variations to said transducer element, and

indication means operably connected to said transducer element and responsive to signals emitted therefrom to provide an indication of the fluid flow variations.

2. Apparatus as set forth in claim 1 wherein said focusing element is flexible and is aflixed to said transducer element whereby said focusing element attains a concave curvature upon inflation of the bag member.

3. Apparatus for monitoring vascular pressure variations, comprising a cuff with fan inflatable bag member positioned therein, said ouff adapted for encirclement about a portion of a cardiovascular subject to restrict the flow of blood in such portion when the bag member is inflated,

a transducer element positioned within said cuff against the side of the inflatable bag remote from the subject, and

a focusing disc in abutment with said transducer element on the side of said element remote from the bag member to reflect pulse energy from the variations in blood flow to reinforce the pulse energy affecting said transducer element.

4. Apparatus as set forth in claim 3 wherein said transducer element is an electronic pressure transducer which produces an electrical signal in response to deformation caused by variations in blood flow.

5. Apparatus *as set forth in claim 4 wherein said focusing disc is a thin disc of flexible material which assumes a concave curvature when the bag member is inflated to provide a focused reflective surface for blood pressure waves.

6. Apparatus as set forth in claim 5 further including a grid attached to said focusing disc to retain said focusing disc in position within said cuff.

7. Apparatus as set forth in claim 6 wherein said disc has flexible tab members for releasably securing said grid to said disc.

References Cited by the Examiner UNITED STATES PATENTS 1,089,122 3/1914 Faught et al. 128-.2.05 2,405,265 8/ 1946 McAlpine 128-205 X 2,896,610 7/1959 Speelman 1282.05 3,239,696 3/ 1966 Burkhalter 128-2.05 X

RICHARD A. GAUDET, Primary Examiner.

SIMON BRODER, xam ner. 

1. APPARATUS FOR MONITORING VASCULAR PRESSURE VARIATIONS, COMPRISING CONSTRICTING MEANS ENCIRCLING A PORTION OF A VASCULAR SUBJECT, SAID CONSTRICTING MEANS COMPRISING A RETAINING MEMBER, AN INFLATABLE BAG MEMBER WITHIN THE RETAINING MEMBER AND MEANS FOR INFLATING THE INFLATABLE BAG MEMBER, A TRANSDUCER ELEMENT POSITIONED WITHIN SAID CONSTRICTING MEANS BETWEEN THE BAG MEMBER AND THE RETAINING MEMBER AND RESPONSIVE TO FLUID FLOW VARIATIONS TO EMIT A SIGNAL PROPORTIONAL THERETO, A FOCUSING ELEMENT POSITIONED ADJACENT SAID TRANSDUCER ELEMENT ON THE SIDE OF SAID TRANSDUCER ELEMENT REMOTE FROM THE INFLATABLE BAG FOR REFLECTING ENERGY FROM THE FLOW VARIATIONS TO SAID TRANSDUCER ELEMENT, AND INDICATION MEANS OPERABLY CONNECTED TO SAID TRANSDUCER ELEMENT AND RESPONSIVE TO SIGNALS EMITTED THEREFROM TO PROVIDE AN INDICATION OF THE FLUID FLOW VARIATIONS. 